Since I haven't touched the DLC (Masakado's Shadow DLC feels so difficult since you will be counting on Uriel's 15 hit skill - among other skills to strengthen it), I think Raven of the Underground (Law route, optional quest) is my favorite.
It is requested by Gabriel, to slay a 'fallen' angel because of his different opinion about God's nature (and so, the Four Archangels' judgment toward mankind) - Mastema.
It gave me vibe since both angels - the Archangels group vs Mastema - have different understanding about God, so you could not really decide whether God in SMT IV is cruel (except when you mention THAT Ancient of Days DLC quest).
In my opinion, Mastema is going neutral here (as opposed to Strange Journey - but still, he's fickle as always). His appearance and this quest made Law route worth, I think, because he made me think over and over.
Anyway, you can hear Mastema's opinion toward your chosen path (Neutral and Chaos included) by visiting him. It's inspiring.